[RFI] Noise Level During Power Outage

[Jim Brown]

On 1/31/2023 9:21 PM, K9MA wrote:
> My QTH is in an older residential area, surrounded by overhead power 
> lines. Line noise is a constant problem. We recently had a major power 
> outage, so I measured the noise levels to get a baseline with little 
> line noise.

Hi Scott,

How do you know that it's line noise, not electronic noise? 25 years 
ago, line noise was a good assumption for anything we heard on the 
bands, but in almost any developed area, the average home has a couple 
of dozen electronic sources, everything from switch-mode power supplies 
for everything that plugs into the wall, variable speed controllers for 
motors, computers and lots of other stuff with microprocessors in them, 
and on, and on. When the power goes out, so do all of those electronic 
noise sources (except for those that UPSs keep running).

The slides for talks I've done at Pacificon, Visalia, and to some clubs, 
show how to use a well-adjusted waterfall to differentiate between 
impulse noise (which is what line noise is) and electronic noise.

http://k9yc.com/KillingReceiveNoise.pdf

Yes, those with ear experience can nearly always tell the difference.

NK7Z has wonderful advice and resources on his site about using 24 hour 
very wide waterfalls to yield clues about operating hours of both 
impulse and electronic sources, and also recognizing multiple electronic 
sources.

73, Jim K9YC